A rotary valve actuator for activating a rotary valve is known that is mounted on the valve and provides a rotational force that changes the valve opening.
A conventional rotary valve actuator is shown in FIG. 4 of Japanese Utility Model Kokai Publication No. Hei 6-1951, for instance. This actuator has an output shaft adapted to be coupled through a joint to an operation shaft of an opening/closing valve at chamfered portions of these shafts when the actuator is mounted on the valve. The actuator is securely mounted on the valve by tightening them by using a bolt and nut, with the bolt inserted through mounting bores formed individually in flange portions of the actuator and the valve.
Another conventional rotary valve actuator is disclosed in FIG. 1 of Japanese Patent Application Kokai Publication No. 2000-193129, for example.
This actuator is provided at an end portion of its output shaft with a fitting groove to which a split ring is fitted. On the other hand, a valve has a bracket formed with a shaft cylinder portion that permits the actuator's output shaft to pass therethrough. The bracket is also formed at its prescribed portion with an engaging groove to which the split ring is engaged. When engaged in the fitting and engaging grooves, the split ring serves to prevent the actuator from coming off the valve.
In order to detach the actuator from the valve for maintenance for example, the actuator is pulled to widen the diameter of the split ring, whereby the engagement between the fitting groove and the split ring is released, so that the output shaft of the actuator can be pulled out of the shaft cylinder of the bracket.
In case of the former rotary valve actuator, it is necessary to utilize a tool such as a screwdriver at the time of detachment of the actuator since the actuator is mounted on the valve by using a fastening tool comprising a bolt and nut. The detaching operation costs work, especially in case that the actuator and the valve are installed near an indoor ceiling, for example.
On the other hand, in the case of the latter rotary valve actuator, a tool such as a screwdriver is not required for the detachment of the actuator since the actuator is mounted on the valve merely by elastic force of the split ring. However, if the prescribed or greater axial external force is mistakenly applied to a housing of the actuator, the actuator comes off the valve. Also in another embodiment illustrated in FIGS. 4-9 of Japanese Patent Application Kokai No. 2000-193129, any tools are not required at the time of the attachment or detachment of the actuator, but a nut has to be rotated many times, so that the workability is poor.